The acute effects of shear rate maniuplation on vascular function in a healthy population

Disease of the cardiovascular system is responsible for the majority of worldwide deaths. The progression of atherosclerosis is pertinent to increased risk of an acute coronary event. An understanding of all factors that contribute to the formation of atherosclerotic plaque is essential for future primary and secondary prevention of cardiovascular diseases. It is now well established that shear rate (SR), the quotient of blood flow velocity and vessel diameter, is responsible for both positive and negative adaptation of the vasculature. Previous data has identified that inflation of a cuff around the forearm induces an increase in retrograde SR, which is detrimental to vascular function. Despite previous data highlighting the acute negative effects of distal cuff inflation on vascular function, little is known about the effects of proximal cuff inflation. Data from study 1 of this thesis indicates that proximal cuff inflation alters SR pattern to a similar degree as distal cuff inflation. However, vascular function, as measured by the established technique of flow mediated dilation (FMD) and the novel technique of low-flow mediated constriction, was not significantly attenuated in the proximal condition. This contrasts with the impacts of distal cuff inflation, which mirrored previous findings. The results from study 1 informed study 2, where a venous occlusion plethysmography (VOP) protocol was performed. Venous occlusion plethysmography has been widely used in research and clinical settings to assess blood flow in the periphery. The universal assumption that arterial inflow is not altered during VOP was questioned. The findings suggest that arterial inflow is, in fact, reduced during VOP. Moreover, it was found that retrograde SR was significantly increased. However, this did not impact upon vascular function as measured by FMD. In summary, despite previous evidence that prolonged and persistent increase in retrograde SR is detrimental to vascular function, neither proximal cuff inflation, nor VOP protocols, negatively affected arterial function. These novel findings highlight the complexity of haemodynamic physiology and suggest that factors other than retrograde SR may influence acute vascular function.

Name dc:type.qualificationname

mphil

Level dc:type.qualificationlevel

masters

Grantor dc:publisher.institution

Liverpool John Moores University

Year dc:date.issued

2014

Author dc:creator

• Humphreys, R

Contributors dc:contributor

• Dawson, Ellen
• Cable, Timothy
• Green, Daniel

• QP Physiology

DOI dc:identifier.doi

https://doi.org/10.24377/LJMU.t.00004568

OAI identifier oai:identifier

oai:researchonline.ljmu.ac.uk:4568